Fifty-three scientists have written to the UN's World Health Organization Director General Margaret Chan cautioning her not to classify e-cigarettes as tobacco products, which would then lead to stricter regulatory controls on the nascent industry.

The scientists say that e-cigarettes are "part of the solution" to worldwide tobacco addiction.

"These products could be among the most significant health innovations of the 21st century — perhaps saving hundreds of millions of lives. The urge to control and suppress them as tobacco products should be resisted," they said. "Policies should be evidence-based and proportionate to risk, and give due weight to the significant reductions in risk that are achieved when a smoker switches to a low risk nicotine product."

Leaked documents demonstrate that the WHO views electronic cigarettes as a "threat" to global health and desires to classify them as regular tobacco products under the Framework Convention on Tobacco Control (FCTC); 178 countries are party to the agreement, and regulation could threaten some of the $3 billion in worldwide sales posted in 2013. Big Tobacco for once is backing the scientists, insisting the devices allow smokers to have a less-risky alternative. (Major cigarette companies, of course, see e-cigarettes as both a major potential competitor and the future of the industry.)

The background: Science doesn't adequately understand the potential health effects of e-cigarettes. One major literature review by researchers from the University of California, San Francisco, found that 84 studies provided no evidence that e-cigarettes help regular smokers quit. "Many people are using e-cigarettes because they are hoping to quit smoking. Smokers who use e-cigarettes are actually less likely to quit smoking than smokers who aren’t using e-cigarettes," says lead author Stanton Glantz. Other researchers say that e-cigarettes are also used in tandem with regular ones, making it very unclear whether they're useful in smoking cessation.

On the other hand, a London study surveyed 5,863 smokers over five years and found that e-cigarette users were 60% more likely than those who used other over-the-counter solutions to quit. The results found that 20% of e-cigarette users were no longer using traditional cigarettes, compared with 8% of users who used other products and 17% who used nothing at all and just went cold turkey.

Study author Jamie Brown is "cautiously optimistic" about the potential harm-reduction uses of e-cigarettes but "the trade-off is we cannot definitively rule out that an unmeasured factor may have influenced the result."

A more recent study published in the journal Tobacco Control surveyed 60 daily smokers aged 18-35 and found that passive exposure to e-cigarettes was associated with a significantly higher desire and urge to consume both e-cigarette and real cigarette smoke.

"It's important to note that there could be effects of being in the company of an e-cigarette user, particularly for young smokers. For example, it's possible that [it] may promote less quitting," says lead author Andrea C. King, director of the Clinical Addictions Research laboratory at the University of Chicago. "The results provide the first evidence in a controlled setting that [e-cigarette] exposure may evoke smoking urges in young adult daily smokers," the authors of the research say.

For some, the potential benefits of e-cigarettes far outweigh the harms, and there's no evidence that regulating them as harshly as real cigarettes would be beneficial to society. "There simply is no product on the market that's more dangerous than tobacco cigarettes, and nobody in their right mind would argue that cigarette smoking is less hazardous or even equally hazardous to vaping," said Michael B. Siegel, a community health sciences professor at Boston University who specializes in tobacco control.

Big Tobacco is big on whatever allows them to keep selling tobacco products en masse and are keen to reform their terrible public image by supporting harm reduction technology. Scientists for the industry are working on harm reduction devices like an electronic sleeve that burns tobacco at a lower temperature, supposedly preventing harmful tar from entering the lungs.

Analyst Richard Essex says that "hard qualitative analysis showed that political, social and economic factors are now major challenges for" tobacco companies. And while these giants would obviously prefer that people keep buying the 6 trillion traditional cigarettes sold worldwide each year, major tobacco companies like Philip Morris see huge survival and growth opportunities in electronic smoking devices.